Diseases of the spine cause significant morbidity. These diseases include abnormalities of the vertebrae, the intervertebral discs, the facet joints, and connective tissue around the spine. These abnormalities can be due to a number of causes, including mechanical injury or degenerative disc disease. Such abnormalities can cause instability to the spine, allowing the vertebral column to become misaligned and producing micromotion between adjacent vertebrae. Vertebral misalignment and micromotion may result in wear to the vertebral bony surfaces and ultimately cause severe pain. Further, these conditions are often chronic and progressive problems.
The treatments for spinal disorders can include long-term medical management or surgery. Medical management is generally directed at controlling the symptoms, such as pain, rather than correcting the underlying problem. For some patients, this may require chronic use of pain medications, which may alter patient mental state or cause other negative side effects.
Recently, a variety of interspinous stabilization devices have become available. These devices may be implanted between the spinous processes of two or more adjacent vertebrae. By stabilizing the spinous processes in this way, significant stress may be taken off the intervertebral discs to prevent disease progression or to improve conditions such as spinal stenosis. In addition, vertebral motion may be controlled without severely altering spinal anatomy.
Currently available interspinous stabilization systems can be secured between adjacent spinous processes using a number of different mechanisms. For example, such devices can include sharp barbs or other surface projections that engage the bony surface of a spinous process. In addition, flexible ligaments or sutures can be placed around the implants and adjacent bone. However, it may be desirable to provide a more rigid and secure attachment to the spinous processes. For example, a rigid attachment may be desirable to prevent the interspinous device from migrating or slipping out of position. In addition, a rigid attachment may be desirable to limit movement and promote fusion at a selected vertebral level. Even further, it may be desirable to provide a device that can also fit interlaminarly between adjacent vertebrae, thereby enhancing the stability of the region.
An interlaminar-interspinous vertebral stabilization system that can be easily implanted and can be securely attached to the spinous processes while being seated interlaminarly is disclosed in U.S. Pat. No. 7,922,750. The vertebral stabilization system utilizes a bone fastener to secure the system to bone. The bone fastener comprises two separate, engageable components that are assembled together during the implantation process. An insertion tool, along with a tightening instrument, is provided for the assembly of the bone fastener.
It would be desirable to provide an improved insertion tool that can be used to assemble the bone fastener of this system, as well as other systems, having a slim profile for ease of use. It would further be desirable to provide such an improved insertion tool enabling a shorter assembly time while also being compatible with the same components and tools available with this system.